Afraid of being stuck on the rock? Well, you're not.
A wide selection of boat services connects you with the mainland or the neighbouring islands, from where you can catch a bus, train or airplane to your next destination.
The transport ranges from slow night boats, big express boats and speed boats to several high speed catamarans.
Due to heavy weather and high waves (especially from Oct-Dec) boat trips may be delayed or cancelled, sometimes even for days, better observe weather forecasts and maybe leave a couple days earlier than needed, or you might, well, get stuck after all. (same goes for visa trips)
For a visa extention, you can make a day trip to Samui to the immigration office; a border run to Hat Yai via Suratthani takes 3 days or you can go in1 1/2 days via Chumphon to Ranong, with mini-bus services. For details ask expats.
Plenty professional travel agents will provide you with any service needed, incl. visa tours. Budget airlines, like AirAsia, offer now convenient 'boat-bus-plane' joint tickets to most popular destinations, like Bangkok, Phuket, Krabi, Hat Yai.
The timetables here give an overview of the current situation, but please double check every detail when purchasing the ticket, as times are subject to change because of weather conditions, seasonal demand or maintenance.
You need to reconfirm 1/2 hour before departure to avoid being replaced with stand-by clients.